Electrically-operated vibratory devices such as are used in the recording or reproduction of sound



Sept. 2, 1930. 1,774,681

M. TROUTON ELECTRICALLY OPERATED VIBRA'I'OHY DEVICES sucu AS ARE USED IN THE RECORDING on REPRODUCTION OF somm Filed Dec. 11. 1928 Patented Sept. 2, 1930 UNITED- ST TES PATENT or'r c nannies neuron, or connma'ron, ENGLANRYASSIGNOR 'ro WIRELESS MUSIC ammo, OFIIQONDON, ENGLAND ELEcrRIcALLYormm'mn v'mna'ro'nv: navicias sucn'As ARE nsiinfm THE m'zconn mtr'omma'rnonuc'rron F scum) application filc'd new, ;11, 192 8,=Seria1-1o. 325,334, and in Great Britain "January 30, 1928.

The present invention relates to electrically operated vibratory devices, such foiriia'mple, as areused in the recording or reproduction of sounds.-. .The inventioiiis concerned 5 with thattype of vibrator "device in the vibratory rn otioii is at' eastpirtiallyio- 'tational about it real or' virtual 'iixis and jn which thearinatuie l'en hin a'difectiouperpendicular-t'o'the axis is at least a's' gi'e'at as the distance of the nearer end f the arm'- me rom t e x v. i

It Shani be; note'd that in this s ecification theword armature is intended to cotterthat pattflof thefvibratory'iuembe'i which .lieS

op ositej to'and co-operates witli'a niag'net po e surface and the end of thejariiiat'uie nea erthe xis of rotation will be referrd to asfth' he'e'l arms armature and thefoppositej e'iid'as' the min set; It na rie'cently been disc vered thn whe an armature of this 6 is of sinifi ienrlen i-ili in rotation toic's ams of rotation;

be made of thel hang iii-th distribution of the ma netic pun-between tliefarrnatnre and a magnet pole s'nrface, due to change injsnap'e of the armature which takes lacennder the influence of the ma 'netic and other forces.

If the vibrator is in t 1e form of a lain cantilever reed, a has" commonly been the case hitherto, difficulty has been eziperie'nced in providing a sufficiently stiff reed which will not become overstressed even when vibratingat relatively large amplitudes and still obtainin'ga sufiiciently flexible armature.

36 The provision of-a relatively sti fi portion between amember providing the mechanical restoring, forceand the armature, however, ensures that the change inshape shall be confined almost entirely to the armature itself. According to the present invention the vi bratory member ot a vibratorydevice comprises-an armature of magnetic material and means for mounting the armature for rota- 5 tion about an axis, that portion ofthe' vibratory member which lies betweenthe axis of rotation im'dthe' hcelof the armature being stiffin relation to the armature itself;

The invention, a form su-itablefor use so in connection with the motor element of a loudspeaker, is illustrated by way of example in the accompanying drawing-in which Figs. land 2 are views in perspective and plan respectively of one form of the invention and f Figs. 3 and 4 are perspective views of alternati-ve forms of the invention;

' Referring to Figs. 1 and 2 the vibratory member comprises a cross-bar 6 adapted to be rigidly clamped at its two ends by means of screws d to pillars e which are rigidly screwed to the base of the instrument, which is'not 'shown.- Projecting at right angles from the cross-bar I), and preferably integral therewith, is an armature 'a'of rectangular cross-section, and a portion j which is still, so far as bending isconcerned, in relation to the armature ais interposed between the cross-bar b and the armature a. The crossbar I) is adapted to twist whenthe armature vibrates'andthus furnish thejrequired restoring force. The-armature can" be regarded as vibrating aboutfan axis 2' coincident with the centre line of the cross-bar Z:. The stiffening may take the. form of webs o'r, since additional mass close to the axis of vibration is often not of great consequence, the additional stiffness may,'a's shown, he obtained by simply using a greater thickness of metal.

1 The vibratory member above described is adapted to be used in an clectro-magnetic vibratory device, such as a loudspeaker motor element, in which the armature is' mounted for vibration toward and away from a pair of magnet poles S (Fig-T4) situated upon one side of the armature. The armature portion of the vibrator extends from the toe to the heel gand this portion lies above and cooperates with the magnet poles. The directi'on of the steady magnet pull is indicated by the arrow h. It is usually desirable that the cross-barb shouldnot bend to anygreat extent and its cross-section is therefore prefer'ably elongated in a vertical direction as shown that is to say in the direction of the magnetic pull. For convenience in manufactare, the under surface of the cross-bar and the under surface (that is the working surface) of the armature are preferably in the same plane as illustrated.

The effect of the still'ened portion in the vibratory member above described in detail is to cause the restoring force due to the torsion of the cross-bar to act, in eil'ec't, substantially as -it it were appliefdQat theheel of the armature.

A connection rod m, or other suitable means,- mayhgpmfidfi. .99 l -hUnfit? with the load (such as a diaphragm) which it is to drive or by which it is to be driven. The point of-iconnection .of the load togthe armature is preferably disgosed'between-the centre and the heel of the armature and a suitable position forthi's point has been found to be between one-third and two-fifths of the length of the armature measured from the heel thereof. 1 j

It will be clear that equivalent results can be obtained in many cases bypivoting the armature and applying the necessary rest0ring force in any known or'suitable manner.

One such arrangement is-illustrated injF 3.- "The' armature a; is mounted on suitable pi ots (not shown) for vibration about theax'is'i,

" the portion jbetw een the heel g of the armature and theaigisi being stiffened as before. A blade kprojeet's downwardly from the stiffened portion j and bears against a screw Z. Theiblade kefurnishes the restoring force and by. rotating the screw l, the airgap between the armature a and 'the fpole pieces (not shown), which aredisposed beneath it, can be adjusted. It will be evidenfi'tl'i'at the blade I: can project 'in"any. convenient direction, for example 'in the'opposite direc tion to the armature a. f I I In some cases difficulty is experience-:1 in the arrangement of Fig. 3 due to chatter between the blade k andthe adjusting screw Z. This difficulty may be overcome by the arrangement shown in Fig. 4 which has also certain other advantages. In this arrangement the two supporting pillars e are united by a yoke which is rovided with a lug n. The vibratory mem er is of the form described in connection with Figs. 1 and 2 excepting that the stiffened portion 1' is here shown with a straight contour. To the upper end of the portion 7' is attached a thin threaded rod 7) which passes through a hole in the lug a and is provided with an adjusting knob q threaded thereon. The hole in the lug 'n isarranged somewhat below the level of the to) of the member I) so that the rod 7) is sub1ected to bending. By screwing up the knob qa twisting moment is applied to the member b and by this means the air gap between the arma tnre a-and the magnet poles can be adjusted. Since some stress always remains in the rod p, even when the screw q is removed, chatter between the rod and the sides of the hole through whichit passesis avoided.

In some cases it may be found that in order to obtain a sufiiciently flexible armatu re its thickness has to be reduced more than 1,774.,esi

may be desirable from other considerations, for example, a. certain thickness is required to prevent saturation of the armature. In such cases the armature may be provided with slots, saw ats;o 'c c1-rpgati onin [direction substantially parallel witli the' 'direittion of the magnetic flux in the armature and in the 1 rr em s l r ed-the.s tsii ls a beparal-lel to tl e axis of rotation of the armature. The armature in Figs. 1 and 4 is, for example; provided with grooves 'I-he:e f *fect of the grooves or corrugations to provide increased flexibility of the armature without substantially--affecting the' eross section of the magnetic flux path through ,t he armature. rlaim H. 2 a :1. electromagnetic vibratory device .comprising.aineriiber inountdjfoi' merr vibration about an axis, an" armarurseon niected said member, a magnet pole and cooperating surfaces onv said a'rniatui ef and magnet pole, the length of said 'surfaees in a'dire'etion normal tosaid axis being 'atil'east as great'as the distance or the nearer'end thereof from said axis, and 'n en'iberfbe ing'stili' in'relationto said mama... 2. An electromagnetic vibratory: devi' comprising .a torsion member clamped both ends, a member'projeeting's ibs antia lly at right"angl'es fr om and eonneete to said torsion member, a'n armature connected l to said torsion member and said projectin teal: ber being stifi" in relation to armatu'itel 3. An electromagnetic y'b device comprising a torsion mem clamped at both ends, a m'enil ,-er projecting siibstai'itially at rightangles from and connected to said torsionfmembenan armature 'com eeted to saidproject'ing member, a magnet pole and eooperatin'g surfaces on said armature and magnet p0 e,'the length of said surfaces in a directionlino'rma'l to said torsion ine'imber be; ing" at least as'g'reat as the ,distanc'c bf the nearer end thereof troin theehjtfli'ri 0f s'aid torsion'inember, said armature beingol substantially'constantthickness and-tlie'aver age thickness of 'said -projecting member being greater than that ef-saidarmature.

An armature'and a magnet pole-adapted to cooperate witasaid armature anrlto pass magnetiefiux through a flux-carrying portion thereof wherein the cross seet-ional area of said flux carrying: portion'insuceea sive selected planes-parallel tosaidflux-is alternately greater and less. v 5 .5

5.v Anarmature and a magnet pole adapted to cooperate withsaidarmature-and to pass magnetic flux through a flux carrying portion thereof wherein the side of said flux carrying portion remote from said magnet pole is grooved in a direction parallel to the direction of said magnetic flux.

(3. A vibratory member comprising means for mounting said member for vibration about an axis and an armature of magnetic material projecting at right angles from said axis, said armature being grooved in a direction substantially parallel to said axis.

7. A vibratory member comprising an elongated n'iember, an armature, a flexible member connected to said elongated member, said armature and said flexible member projecting from substantially the center of said elongated member in different directions, and connecting means attached to said arma ture intermediate the ends thereof.

8. A vibratory member comprising an elongated member, an armature, a flexible member connected to said elongated member, said armature and said flexible member projecting substantially perpendicularly from substantially the center of said elongated member in different directions, and connecting means attached to said armature intermediate the ends thereof.

9. A vibratory device comprising a member mounted for rotary vibration about an axis, an armature, a flexible member connected to said rotatably mounted member, said armature and said flexible member projecting in different directions from substantially the center of said elongated member, and connecting means attached to said armature intermediate the ends thereof.

10. A vibratory device comprising a torsion member clamped at both ends, an armature, a flexible member, said armature and said flexible member being connected to said torsion member and projecting in different directions therefrom, and connecting means attached to said armature intermediate the ends thereof.

11. An electromagnetic vibratory device comprising a member mounted for rotary vibration about an axis, an armature connected to said member, a magnet pole adapted to co-operate With said armature and a flexible member connected to said rotatably mounted member and projecting therefrom in a different direction from said armature, the end of said flexible member further from said axis being prevented from vibrating.

12. An electromagnetic vibratory device comprising a member mounted forrotary vibration about an axis, an armature connected to said member, a magnet pole adapted to co-operate With said armature, a flexible member connected to said rotatably mounted member and means for applying variable tension to said flexible member.

13. An electromagnetic vibratory device comprising a member mounted for rotary vibration about an axis, an armature con- MAURICE TROUTON.

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